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Fractional Excretion of BicarbonateAka: FE-HCO3

Indications
1. Differentiate Proximal RTA from Distal RTA
2. Requires that serum bicarbonate be normal
Calculation
1. FE-HCO3 = (uHCO3 x sCr) / (sHCO3 x uCr)
2. Annotation
  1. Where FE-HCO3 is fractional excretion of bicarbonate
  2. Where uHCO3 is urine bicarbonate
  3. Where sHCO3 is serum bicarbonate
  4. Where uCr is Urine Creatinine
  5. Where sCr is Serum Creatinine
Interpretation
1. FE-HCO3 <5%: Distal RTA
2. FE-HCO3 >15%: Proximal RTA
  1. Assumes serum bicarbonate >20 meq/L

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This page was written by Scott Moses, MD. This page was last revised before 5/10/08, prior to consistent tracking of revision date. This page was last published on 6/1/2008. Please send comments and questions to the editor. Contact information may be found on the page About the Family Practice Notebook. These pages are best viewed with Microsoft Internet Explorer 6.0.